Peritoneal artificial kidney

ABSTRACT

A PERTIONEAL ARTIFICIAL KIDNEY IN WHICH A PREPARED SOLUTION IS CIRCULATED THROUGH THE PERITONEAL CAVITY AND THE RESULTING PERITONEAL FLUID CONTAINING UNWANTED TOXIC METABOLITES IS WITHDRAWN FROM THE THE CAVITY AND PASSED THROUGH FILTRATION MEANS THAT PERMITS ESSENTIALLY ONLY   PASSED OF PURE WATER WHILE REJECTING THE METABOLITES. THE FILTERED PERITONEAL FLUID IS THEN RECONSTITUTED WITH A CONTROLLED MAKE-UP SOLUTION FOR RECYCLE TO THE PERITONEAL CAVITY AND THE REJECTED RESIDUE IS DISCHARGED AS WASTE.

July 23, 1974 C BRQWN ETAL 3,825,493

PERI'I'ONEAL ARTIFICIAL KIDNEY Filed Sept. 29, 1972 RECON STITUT NG SOLUTION PRESSURE REGULATING VALVE METERING PUMP IMPLANTED PERITONEUM 26\- CATHETER 2 HIGH PRESSURE PUMP PERITONEAL CAVITY RECONSTITUTINGL SOLUTION MEMBRANE PERITONEAL FLUID United States Patent 3,825,493 PERITONEAL ARTIFICIAL KIDNEY Clinton E. Brown, Silver Spring, Md., and Moshe-Aharou Frommer, Rehovoth, Israel, assignors to Hydronautics, Incorporated. Laurel, Md.

Filed Sept. 29, 1972, Ser. No. 293,474 Int. Cl. B01d 31/00, 13/00 US. Cl. 210-23 7 Claims ABSTRACT OF THE DISCLOSURE A peritoneal artificial kidney in which a prepared solution is circulated through the peritoneal cavity and the resulting peritoneal fluid containing unwanted toxic metabolites is withdrawn from the cavity and passed through filtration means that permits essentially only passage of pure water while rejecting the metabolites. The filtered peritoneal fluid is then reconstituted with a controlled make-up solution for recycle to the peritoneal cavity and the rejected residue is discharged as waste.

This invention relates to artificial kidneys for removing toxic substances in the blood normally excreted through the human kidney, and more particularly, to a compact, wearable artificial kidney for removing the toxic substances by peritoneal dialysis.

In recent years, the development of artificial kidneys has prolonged the lives of human beings with damaged or inoperative kidneys. The physiology of the human kidney is fairly well understood and involves the removal of nonvolatile wastes from the blood stream and the continuous regulation of the blood composition such that the conditions in body tissues necessary for the life of cells are maintained. Accordingly, when the kidneys are not operating properly, these functions must be performed by artificial means to prevent any imbalance from developing and the build-up of toxic conditions in the blood.

A variety of artificial devices has been developed for assuming the function of a human kidney. Most commonly, these devices withdraw blood from the body and pass the blood through an external dialyzer to draw out or remove the undesired toxic substances from the blood and then the blood is returned to the body. When these devices are used for several hours, several times per week, they are capable of reducing the level of concentration of toxic substances in the blood to a safe level.

The dialysate or wash solution, however, must be carefully formulated so as to be isotonic to the blood and so that certain desirable constituents of the blood, such as electrolytes, are not lost in the dialysis procedure. The devices all commonly operate on an intermittent basis, requiring a high volume of dialysate and in turn necessitating a bulky and immobile reservoir for the solution. Further, the intermittent use of such devices causes the concentrations of toxic substances in the patients blood stream to oscillate from an abnormally high position just prior to treatment to a low point immediately following treatment. This creates undesirable side effects in the patients general condition. Finally, the fact that the blood is being used for the treatment involves the risk of clotting and anticoagulants must be utilized in the treatment.

Accordingly, more recent efforts in the field of artificial kidneys have been to develop devices that can operate independently of the blood and that can consistently maintain the concentration of toxic substances at an acceptable level. In order to provide a continuously operating kidney, of course, the devices must be portable and wearable by the patient and desirably compact, reliable, and of minimum discomfort.

In US. Pat. No. 3,799,873 of Clinton E. Brown, for

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example, which patent is assigned to the assignee of the present invention, there is described a completely recirculating artificial kidney, suitable for use in removing toxic substances from the blood by peritoneal dialysis. The device operates on the well known technique of peritoneal dialysis, in which a prepared solution is circulated through the peritoneal cavity and the unwanted metabolites, such as urea, creatinine, uric acid, etc. are drawn into the solution by natural diffusion from the blood stream across the peritoneal membranes, resulting in what is commonly referred to as peritoneal fluid. This fluid now containing the unwanted toxic substances is removed from the body, and passed through an external dialyzer to remove the toxic substances from the peritoneal fluid, and the purified fluid is then returned to the peritoneal cavity. To provide a completely portable device, however, means are also provided for purifying, reconstituting, and re cycling the dialysate for the external dialyzer. In essence, the device comprises two recirculating loops; one for the body fluid and one for the dialysate.

While this represents a significant improvement in the art of developing wearable, compact, and efl'lcient artificial kidneys, it obviously involves more operations than the more common intermittent, but immobile, devices heretofore used to dialyze the blood. In accordance with the present invention, however, there is provided a much more simplified artificial kidney that requires only one recirculating loop like a blood dialysis device, but without the necessity of doing something with the spent dialysate that has heretofore plagued the development of a truly satisfactory mobile device. More specifically, it has been found that the need for an external circuit to cleanse the dialysate in order to provide a portable device can be eliminated by filtering the peritoneal fluid of its toxic substances and returning the filtered fluid after being reconstituted to the peritoneal cavity. Thus, in contrast to earlier intermittent devices where the dialysate is discarded, or portable devices where the dialysate must be purified and recirculated, the device of the present invention filters the peritoneal fluid and returns it for further use.

As embodied and broadly described, therefore, this invention comprises circulating a prepared solution through the peritoneal cavity to withdraw toxic metabolites from the blood across the peritoneal membranes and into the solution forming peritoneal fluid; removing the peritoneal fluid from the peritoneal cavity; filtering the fluid to remove toxic substances from the peritoneal fluid; reconstituting and recycling the filtered fluid back to the peritoneal cavity; and discarding the rejected wastes.

Of the accompanying drawings:

FIG. 1 illustrates a schematic representation of the peritoneal artificial kidney of this invention; and

FIG. 2 is a suitable filter cell employing reverse osmosis membranes.

The artificial kidney of this invention is particularly adapted for use with peritoneal fluid. By peritoneal fluid is meant not only that fluid naturally existing in the peritoneal cavity, but the prepared conventional peritoneal dialysis solutions added to the cavity to supplement its volume. For a more thorough discussion of peritoneal dialysis for performing the function of a natural kidney and other examples of previous methods for performing recirculation peritoneal dialysis, reference is made to an article by J. H. Shinaberger, L. Shear and K. G. Barry, entitled Increasing Efiiciency of Peritoneal Dialysis," Transactions of American Society of Artificial Internal Organs, Vol. II, pages 76-82, 1965.

With reference to FIG. 1, peritoneal fluid 2 is withdrawn from conventional catheters 4, preferably of silicone rubber, implanted surgically in the peritoneum or peritoneal cavity and forced by the pumping action of a high-pressure pump 6 to the intake side 8 of a filtration means 10. Preferably, filtration means or filter cell 10 in cludes as the filter element 12 a membrane with hyperfiltration characteristics, such as reverse osmosis membranes, mounted within a suitable housing and having inlet means 14 for the peritoneal fluid, toxic metabolite eflluent means 16, both on the same side 8 of the filtration element 12, and a purified filtrate outlet means 18. Cell ber of alternative devices having hyperfilter characteristics that were used to cleanse the dialysate for the external dialyzer.

Peritoneal fluid is fed to filter cell 10 under pressure and at a rate of from to 50 ml./min., where it travels through the cell with a motion parallel to the filtering element 12, emerging as a concentrated solution of low molecular weight solutes or metabolites, such as urea, creatinine, uric acid, and electrolytes from outlet 16. Pressure is maintained on the order of 400 to 600 p.s.i. to pro vide a pressure differential across membrane 12 in filter cell by pump 6, and pressure regulating valve 20 in the waste rejection line 22. Relief or regulating valve 20 is designed to permit a continuous flow of peritoneal fluid through filter cell 10 and a continuous flow of wastes 22 to a urinal 24.

In the usual peritoneal dialysis treatment, Water is also removed in the peritoneal fluid. This is accomplished by providing the solution fed to the peritoneal cavity with sorbitol or a sugar, such as dextrose, to produce an osmotic pressure difference between the body and the solution, causing a flow of water across the peritoneal membranes 1 and into the solution forming peritoneal fluid. Generally,

the metabolites and electrolytes do not pass through membrane 12, but are rejected, and essentially only pure water tion may be added to the filtrate after it leaves filter cell 10 or, preferably, and as schematically shown in FIG. 1, is added at 19 to the low pressure side 26 of cell 10 and at the opposite end of the cell from peritoneal fluid inlet 14 so that its flow is countercurrent to the flow of peritoneal fluid. By this arrangement, the osmotic pressure of the solution can be used to also assist in the flow of water through membrane 12 of the filter cell.

The reconstituted water 28 is recycled back to the peritoneum through suitable catheters for further removal of toxic substances by peritoneal dialysis.

High pressure pump 6 and metering pump 32 are preferably cam driven by a suitable electric motor which is in turn powered by a portable, re-chargeable battery to pro- 1' vide a convenient wearable system. The pump and metering system are conventional and are more fully described in the above-mentioned patent.

Thus, the present invention provides a wearable, yet compact, artificial kidney uitable for use with peritoneal dialysis that recovers, filters, and reconstitutes peritoneal fluid in use and that requires only a small volume of fluid and a single recirculating loop. Of course, it is to be recognized that it is within the scope of this invention to modify the nature of the power source needed to operate the pump, and any source of power, portable or non-portable, could be used with the invention. Many other modifications are also possible, including fail-safe features to protect against punctures, leaks, ruptures in the fluid lines as well as clogging of the filters, sensing devices to sense the concentration of toxic substances in the recycled peritoneal fluid and the accumulation of waste in the urinal as well as automatic shut-01f and warning devices to alert the patient of any malfunction and the need for service to the system. The invention, therefore, is not limited to the specific details shown and described and departures may be made from such details without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

. 1. A portable and wearable artificial kidney for continuously removing toxic metabolites from the blood comprising means for continuously circulating a prepared solution through the peritoneal cavity to draw toxic metabolites from the blood across the peritoneal membranes and into the fluid in the cavity forming peritoneal fluid; filtration means for continuously removing the toxic metabolites from the peritoneal fluid; means for continuously conveying the peritoneal fluid from the peritoneal cavity to the filtration means; means for continuously, recycling purified filtrate from the filtration means back to the peritoneal cavity; and means for reconstituting the recycled peritoneal fluid to make it suitable for re-use in the peritoneal cavity.

2. The kidney of claim 1, wherein the filtration means comprises a plurality of membranes with hyperfiltration characteristics and means for pressurizing the peritoneal fluid conveyed to the membranes to provide a pressure differential across the membrane.

3. The kidney of claim 2, wherein the filtration means includes a housing having peritoneal fluid inlet means and toxic metabolite eflluent means on the high pressure side of the membranes and purified filtrate outlet means on the low pressure side of the membranes.

4. The kidney of claim 2, wherein the housing also includes reconstituting fluid inlet means for introducing make-up solution to the low pressure side of the membranes in countercurrent flow to the flow of peritoneal fluid on the high pressure side of the membrane.

5. A method for continuously removing toxic metabolites from the blood, comprising continuously circulating a prepared solution through the peritoneal cavity to draw toxic metabolites from the blood across the peritoneal membranes and into the solution forming peritoneal fluid, continuously withdrawing the peritoneal fluid from the cavity, continuously filtering the fluid to remove the toxic metabolites, reconstituting and continuously recycling the filtered fluid to the peritoneal cavity for further use, and withdrawing and discharging the rejected residue as waste.

6. The method of claim 5, wherein the filtered fluid is reconstituted by the addition of a control solution of make-up electrolytes and sorbitol or a sugar.

7. The method of claim 5, wherein the peritoneal fluidis filtered by pressurizing the fluid and forcing it through membranes with hyperfiltration characteristics.

References Cited UNITED STATES PATENTS 3,506,126 4/1970 Serfass et al. 210-96 3,579,441 5/1971 Brown 210321 X 3,545,438 12/1970 De Vries 210-321 X 3,483,867 12/ 1969 Markovitz 210-23 X 3,619,423 11/1971 Galletti et al. 21022 FRANK A. SPEAR, JR., Primary Examiner US. Cl. X.R. 2l0321 

